Thanks guys for the replies!
@rpt007 The simulator is just a fun project, it will probably be in my room, but I don't really know yet. 7cm is just a guess at this stage, I haven't got any dimensions yet but that's my guess. The gauges are circle too, so I think the word you'd be looking for is diameter, not diagonal. Depth isn't an issue no, but I don't want anything ridiculous if you know what I mean.
Some of those Nema motors look pretty good but they're a little bit pricy for just a couple of gauges. However those adafruit ones look pretty nice, very small and cheap. I think I would go with those? What do you think?
@scottyjr Those also look very nice, I've seen them in other videos but again they're just too expensive for a couple of gauges.
@Robin2 Thanks for those links, very useful. Those tiny motors look good but almost too small. Do you think they would actually work? The other one looks good too but the same as most of the others, I feel they are too expensive.